1 - Database Intro

89 busi 335 not all data attributes logically relate

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Unformatted text preview: art Num. relate to the primary key Part Num. Are there any nonkey attributes that are dependent of the other dependent of the other nonkey attributes? The non-key attributes (Name, Address, Tel Num) are not dependent on Part Num Part Num. Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 90 Splitting Unnormalized Tables (cont (cont’d) Splitting Unnormalized Tables Unnormalized Tables BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 91 How to link these two tables? tables? BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 92 Linking Normalized Tables Linking Normalized Tables Steps in Normalization in Normalization • The normalized tables Unnormalized Data (Table with repeating groups) (Table with repeating groups) need need to be linked together so that the data in them can be data in them can be related and made accessible to users. Remove repeating groups First normal form 1NF Remove partial dependencies • The degree of Linking Table BUSI 335 Second normal form 2NF association between tables (i.e. 1:1, 1:M, M:N) determines how the linking occurs the linking occurs. Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo Remove transitive dependencies Third normal form 3NF Refer to pp. 473-478 in Accounting Information Systems by James A. Hall 93 BUSI 335 Example: Unnormalized Student Enrollment Table Enrollment Table Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 94 Step 1: Remove Repeating Groups 1: Remove Repeating Groups PK Can you identify any repeating groups? PK BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 95 BUSI 335 Copyright © 2009-10 Y.M. Cheung, William Tan and Carson Woo 96 Step Step 2: Remove Partial Dependencies Dependencies Step 3: Remove Transitive Dependencies Dependencies • Partial Dependencies occur only in tables with a composite primary key primary key. • The course and instructor data are dependent only on the Course portion of the composi...
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